This invention relates to a pumping device for administering intravenous and intra-arterial liquids. More particularly, this invention relates to a pumping device which includes a valved pumping chamber wherein the inlet and outlet valves are magnetically operable.
The use of an infusion therapy system as a method of treating patients is well known in the prior art. These systems provide health care personnel with the means to administer medication, provide nutrition, prevent dehydration or assure infusion of necessary fluids into the body of a patient. Sterility in infusion therapy is presently maintained by using disposable devices which are sterilized before use and discarded after use thus eliminating the need for expensive, complex, and often uncertain resterilization. The rising cost of health care is a matter of substantial concern to those in need of medical treatment. Any new development must therefore be conceived with simplicity and low cost in mind.
The dosage of medication administered by infusion therapy varies over a wide range of values spread over an even wider range of times. The prescribed dosage of medication per unit of time may be translated into a flow rate for an infusion pump system. Very low flow rates are often characterized by pulsatile spurts of liquid through the infusion delivery system into the patient. This pulsatile flow has disadvantages in that the lumen in the needle used during venpuncture may become closed in the intervals between the spurts of fluid. This closing is caused by blood flowing back into the infusion delivery system through the venipuncture. The ideal situation is therefore to provide a uniform continuous flow of medication into a patient at the lowest possible rate settings for the infusion system employed. This is particularly important with medication having a short half-life such as Oxytocin as sold by Abbott Laboratories. In these situations the infusion system must maintain an appropriate level of medication within the patient's body concurrently with the drop in potency of the medication.
An examination of the fluid mechanics of an infusion fluid delivery system indicates that the fluid pressure within a patient's blood stream works against the intravenous or intra-arterial infusion of fluid. The blood pressure of the patient also has a tendency to cause reflux of blood back into the needle as indicated earlier. If blood remains in the lumen it has a tendency to clot and thereby cause a blockage to the intravenous or intra-arterial infusion of fluid. Hence, the need arises to provide a device which will assure a regulated uniform and continuous one-way intravenous or intra-arterial infusion of fluid into the body of a patient which will overcome the blood pressure of the patient and at the same time assure continuous purging of the needle used for venipuncture. Such a device would also provide a uniform and constant one-way flow to assure a continuous supply of medication or fluid matched to the treatment needs of a patient no matter how small or how large those needs may be.
On the supply or upstream side, not all infusion administration systems are set up in exactly the same fashion. The head or weight of column of fluid acting on the pump is dependent on the size of the equipment being used, the location of the pump in relation to the fluid source and the work habits of the attending nurse or physician. These variables directly affect the upstream pressure perceived by the pump. On the patient or downstream side, the position of the patient with respect to the pump directly affects the downstream pressure perceived by the pump. It is therefore desired to provide an infusion pump system whose operation is only negligibly affected by a change in the supply side or upstream head acting on the pump or a change in the downstream pressure perceived by the pump. Finally, the infusion administration system must prevent the flow of air or gas into the patient. Various designs of electronic and mechanical means associated with infusion fluid delivery systems have attempted to overcome these problems. These various means have often been characterized by complexity of design, difficult use, high cost or the need for complex valving arrangements and actuating mechanisms. In addition, infusion delivery systems must be designed to be quickly operational in order to allow health care personel the greatest amount of time to administer to more important treatment needs of a particular patient.
Proper pump priming is another area of concern for health care personnel. Any pump used in an infusion fluid administration system should both be easy to prime and clearly able to show positive visual indication of having been primed. Additionally, it is desirable to give an indication to the user that all components are assembled correctly. The appearance of a signal, the positioning of components without the exertion of undue force and proper orientation of internal parts supplies the user with the confidence that the infusion administration system is properly set up for operation. Once properly positioned in the pump actuator, primed and operating, there is also a need to give a positive visual indication of operation. Infusion fluids are often clear and when flowing give no positive visual perception of movement. Many pumps used in infusion flow control systems found in the prior art have been hidden from view by operating means or flow controllers. It is therefore an advantage of this invention to provide a pump system whose operation at all but the very smallest flow rates can be visually verified by health care personnel.
It is also an advantage of this invention to provide a disposable pumping chamber for an infusion delivery system with integral valving that is easy to use, simple to manufacture with repeatability and reliability and is low in cost. A further advantage is the provision of an intravenous or intra-arterial delivery system which prevents the flow of air into the patient through a venipuncture site during administration of intravenous or intra-arterial fluid as well as when the source of infusion fluid is depleted.
It is yet another advantage of this invention to provide an infusion pump system which is chemically substantially inert, easily sterilized, nonbreakable, light weight and exceedingly compact. Additionally, an infusion pump system is provided which does not require the sealing properties of gaskets or O-rings for leak-proof operation.
Recent developments have regulated flow control of infusion fluid by the use of electro-mechanical devices; specifically low volume pumps with appropriate valving to assure quick priming and air free flow of fluid. These pump systems utilize pumping chambers generically called "cassettes".
Typical of the developmental work done on cassette designs are U.S. Pat. Nos. 4,199,307 and 4,273,121, and patent application Ser. No. 164,434 filed June 30, 1980, now U.S. Pat. No. 4,456,009, by the same assignee as in this application. Flow control of the pumped fluid is afforded by valves that are actuated by various mechanical and electrical means. Typical of the patents disclosing various valving means in general are U.S. Pat. Nos. 4,126,132; 3,976,402; 3,298,320; 3,559,644; 3,620,650; 4,142,524 and application Ser. No. 278,546 filed June 29, 1981 by the same assignee as in this application. Magnetic valving in intravenous flow systems was disclosed in U.S. Pat. No. 3,890,968 for a gravity system. The positive on-off action of the valves in U.S. Pat. No. 3,890,968 generated the pulsatile flow which this invention specifically avoids.